The invention relates to a DC-DC converter for testing a low-voltage battery, to an electrical drive system comprising a low-voltage network and a DC-DC converter, and to a method for testing a low-voltage battery, in particular in electrically operated vehicles such as electric cars and hybrid vehicles.
It is to be expected that future electronic systems which combine new energy storage technologies with electric drive technology will be used increasingly both in stationary applications, as such as, for example, wind turbines or solar systems, and in vehicles, such as hybrid or electric vehicles.
In low-voltage electrical distribution systems in electrical drive systems of electrically operated vehicles, electrical distribution system consumers such as, for example, brake assist or steering assist functions are supplied power firstly by a low-voltage battery and secondly by a further energy source. The further energy source in conventional vehicles is generally the alternator, while in electrically operated vehicles such as electric vehicles or hybrid vehicles, a DC-DC converter, as further energy source, draws electrical energy from the high-voltage network of the vehicle and feeds it into the low-voltage network. Generally, the low-voltage battery, for example a 12 volt battery, is used as backup and/or for buffer-storing in the case of peak loads, while the main or basic load for the electrical distribution system consumers is borne by the further energy source.
If the low-voltage battery should fail owing to a malfunction or a defect during operation of the electrical drive system, the buffer effect of the low-voltage battery in the case of peak loads is lost. It is therefore necessary to modify the energy management in the low-voltage network in order to stabilize the low-voltage network.
This requires reliable, rapid and safe identification of the failure of the low-voltage battery in order to be able to introduce the stabilizing countermeasures as quickly as possible. The publication EP 2 073 028 A1, for example, discloses a sensor arrangement for a battery, with the aid of which the operating state of the battery can be detected and can be passed on to an energy management system in an electrically operated vehicle. The publication DE 102 19 824 A1 discloses a method for identifying battery-less operation of a vehicle electrical distribution system comprising a generator driven by a motor, a battery, low-voltage consumers and means for voltage evaluation.
There is a need for solutions which enable diagnosis of the low-voltage battery in a low-voltage network of an electrical drive system in a reliable and rapid manner.